/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.zookeeper.server.auth;

import java.util.Enumeration;
import java.util.HashMap;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.zookeeper.server.ZooKeeperServer;

public class ProviderRegistry {
	private static HashMap<String, AuthenticationProvider> authenticationProviders = new HashMap<String, AuthenticationProvider>();

	private static boolean initialized = false;
	private static final Logger LOG = LoggerFactory.getLogger(ProviderRegistry.class);

	public static AuthenticationProvider getProvider(String scheme) {
		if (!initialized)
			initialize();
		return authenticationProviders.get(scheme);
	}

	public static void initialize() {
		synchronized (ProviderRegistry.class) {
			if (initialized)
				return;
			IPAuthenticationProvider ipp = new IPAuthenticationProvider();
			DigestAuthenticationProvider digp = new DigestAuthenticationProvider();
			authenticationProviders.put(ipp.getScheme(), ipp);
			authenticationProviders.put(digp.getScheme(), digp);
			Enumeration<Object> en = System.getProperties().keys();
			while (en.hasMoreElements()) {
				String k = (String) en.nextElement();
				if (k.startsWith("zookeeper.authProvider.")) {
					String className = System.getProperty(k);
					try {
						Class<?> c = ZooKeeperServer.class.getClassLoader().loadClass(className);
						AuthenticationProvider ap = (AuthenticationProvider) c.newInstance();
						authenticationProviders.put(ap.getScheme(), ap);
					} catch (Exception e) {
						LOG.warn("Problems loading " + className, e);
					}
				}
			}
			initialized = true;
		}
	}

	public static String listProviders() {
		StringBuilder sb = new StringBuilder();
		for (String s : authenticationProviders.keySet()) {
			sb.append(s + " ");
		}
		return sb.toString();
	}
}
